Port Wine Stain (PWS) is a congenital, progressive vascular malformation of human skin. Approximately 1,200,000 individuals in the United States have PWS birthmarks. Presently, all PWS are treated using the pulsed dye laser (PDL). However, PWS response remains unpredictable with less than 10% of patients achieving complete fading of their PWS after PDL. Moreover, PWS can recur after PDL therapy due to reformation and reperfusion of PWS blood vessels. The reasons for treatment resistance remains incompletely understood. Inadequate PWS therapeutic outcome is a clinically significant problem that urgently requires a solution. Our central hypothesis in this research proposal is: Activation of angiogenesis pathways induced by PDL therapy is one of the crucial factors that causes the reformation and reperfusion of PWS blood vessels. Therefore, PDL combined with administration of angiogenesis pathways' inhibitors, such as rapamycin (RPM), may potentially improve PWS lesion blanching and thus lead to a better therapeutic outcome as compared to PDL treatment alone. The scientific rationale for this strategy (PDL+RPM) is that PDL is used to induce PWS blood vessel injury while topical administration of RPM can inhibit reformation and reperfusion of PWS blood vessels after laser exposure. The proposed research will focus on targeting the clinical barrier that appears to diminish PWS laser therapeutic outcome, namely reformation and reperfusion of PWS blood vessels after PDL treatment. A series of pharmacological, molecular and biochemical approaches are proposed herein to support this novel approach for PWS treatment: (1) safety and efficacy evaluations and pharmacokinetics of newly developed topical formulations of RPM; (2) the time course of RPM-mediated inhibition on angiogenesis pathways induced by PDL; (3) whole-transcript profiles from intact PWS and lesions after various laser and RPM treatments in an attempt to reveal the molecular mechanisms underlying origination and development of PWS. We expect the proposed studies will advance our understanding of molecular pathophysiology of PWS and improve response to PDL treatment.